(CNSNews.com) -- Organized crime in Mexico fueled the theft of more than 1.8 million barrels of crude oil and petroleum from the nation’s state-run oil company Pemex in the first half of 2012, an 18 percent increase when compared to the same period in 2011, according to the company’s communications office.

Pemex further said that organized criminal gangs and their associates are fueling the “growing” theft of oil despite the state-run company’s best efforts to combat the problem.

Pemex estimated that in the first six months of 2012, the volume of oil removed illegally from its national pipeline system through clandestine taps reached 1,841,478 barrels, marking an 18 percent increase from the 1,557,569 barrels stolen during the same period last year.

According to the company, there are 158.9 liters (an estimated 42 gallons) in each barrel. That means, on average, at least 17,500 gallons of oil (about 426 barrels) per hour were stolen during the first half of 2012.

Pemex production platform off the coast of Mexico. (AP)

There were 111 persons “arrested red-handed for the crime of oil theft” between January and June of this year, according to Pemex.

Most of the oil theft takes place along sections of the national pipeline network that run across the country and at some Pemex refining centers.

Criminals use intrusive devices referred to as “clandestine taps” (CTs) to steal the oil, reported Pemex, adding that a total of 824 intrusive taps were identified in the first six months of 2012.

The areas most affected by oil theft include the Mexican state of Veracruz, where 114 CTs were located, followed by Sinaloa (90 CTs); Tamaulipas (83 CTs); and the states of Sonora and Nuevo Leon where 62 CTs were found at each one.

Violent drug cartels such as Los Zetas are known to operate in those states. The Los Zetas cartel has reportedly been linked to violent armed clashes associated with oil theft.

Several U.S.-based companies operating near the border have been accused of helping Mexican criminals refine stolen oil. Pemex filed a lawsuit against 12 firms, including units of Royal Dutch Shell, according to Reuters.

“PEMEX has strengthened surveillance of its national pipeline network, which has increased the detection of illegal and clandestine taps, decreased the volume of stolen fuel, and reduced risks to the population,” Reyna Zea, a Pemex spokeswoman, told CNSNews.com in Spanish when asked to comment on the growing oil theft problem.

The spokeswoman said she was unable to name specific organized crime gangs involved in stealing oil from Pemex.